Making cellulosic fiber sheets, particularly paper and paperboard, includes producing an aqueous slurry of cellulosic fiber, depositing this slurry on a moving papermaking wire or fabric, and forming a sheet from the solid components of the slurry by draining the water. The slurry may also contain inorganic mineral extenders or pigments. Likewise, organic and inorganic chemicals are often added to the slurry prior to the sheet-forming step to make the papermaking method less costly, more rapid, and/or to attain specific properties in the final paper product. After drainage, the sheet is pressed and dried to further remove water.
The paper industry continuously strives to improve paper quality, increase productivity, and reduce manufacturing costs. Chemicals are often added to the fibrous slurry before it reaches the papermaking wire or fabric, to improve the method drainage/dewatering and solids retention. Such chemicals are called retention and/or drainage aids. Drainage or dewatering of the fibrous slurry on the papermaking wire or fabric is often the limiting step in achieving faster method speeds. Improved dewatering can also result in a dryer sheet in the press and dryer sections, thus requiring less energy. Also, this stage in the papermaking method determines many sheet final properties.
Regarding solids retention, papermaking retention aids are used to increase the retention of fine furnish solids in the web during the turbulent method of draining and forming the paper web. Without adequate retention of the fine solids, they are either lost to the method effluent or accumulate to high levels in the recirculating white water loop, potentially causing deposit buildup. Additionally, insufficient retention increases the papermakers' cost due to loss of additives intended to be adsorbed on the fiber to provide the respective paper opacity, strength, or sizing property.
It is desirable to develop new retention and drainage aids. The present invention is directed to these, as well as other important ends.